The proposed research is an analysis of longitudinal data collected through the Epidemiologic Catchment Area (ECA) Program. 18,572 subjects, probabilistically selected from populations in five geographic areas in the country, were interviewed at two or more points in time with questionnaires including a common sociodemographic section and the NIMH Diagnostic Interview Schedule (DIS). Analysis of these data to date have centered on cross sectional approaches and DIS/DSM-III diagnoses. This proposed set of analyses focuses on: 1) longitudinal approaches; 2) clusters of symptoms from the DIS as well as DSM-III diagnoses; and 3) risk factors. These foci grow directly out of preliminary work by this team of investigators. By the beginning of the award period, both waves of data will be available from all five sites of the ECA Program. Three phases of the analysis are described. In the first phase, population indicators of the force of psychiatric morbidity are conceptualized, operationally defined in the context of the ECA, and estimated. These indicators include rates of: 1) first and total incidence; 2) intensification and acquisition of symptoms; and 3) continuance or termination. In the second phase of analysis, these indicators are used to explore the longitudinal evolution, over the course of one year, of symptoms, symptom clusters or syndromes, and diagnoses. This phase includes the search for useful thresholds and for early onset symptom clusters. In the third phasse of the analysis, the effects of risk factors on the development and continuance of symptoms, syndromes, and diagnoses is addressed. Each phase of the analysis will begin with the Baltimore data set and, often, lead to replications with other sites' data. These analyses address the question as to whether the DSM-III, developed essentially out of clinical experience, is the best nosologic representation of these ECA data, which originate in a community. The analyses will identify risk factors and symptom indicators of early onset which will be useful in future research and prevention efforts. Thus, the proposal focuses on two essential uses of epidemiology: Identification of syndromes; and search for causes.